Method for fabricating semiconductor device

Abstract

In a method for fabricating a semiconductor device, a first region in a semiconductor substrate is formed with a first-gate-electrode formation portion composed of a first silicon film, a second silicon film, and a second protective film, and a second region therein is formed with a second-gate-electrode formation portion composed of the first silicon film, a first protective film, the second silicon film, and the second protective film. Then, the first-gate-electrode formation portion is formed into a first fully silicided gate electrode, and the second-gate-electrode formation portion is formed into a second fully silicided gate electrode.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority under 35 U.S.C. § 119 on Patent Application No. 2006-111001 filed in Japan on Apr. 13, 2006, the entire contents of which are hereby incorporated by reference. BACKGROUND OF THE INVENTION [0002] (a) Fields of the Invention [0003] The present invention relates to methods for fabricating a semiconductor device, and in particular to methods for fabricating a semiconductor device with fully silicided gate electrodes. [0004] (b) Description of Related Art [0005] With recent enhancement of packing density, functionality, and speed of a semiconductor integrated circuit device, a metal gate electrode thereof using a metal material is actively developed. Potential metal gate electrodes to be developed include: a dual metal gate electrode formed of a combination of two types of metal materials with different work functions; and a fully silicided (FUSI) gate electrode the whole of which is formed of metal silicide....

AI Technical Summary

Benefits of technology

[0014] An object of the present invention is to solve the conventional problems described above, and to provide a method for fabricating a semiconductor device capable of accurately forming a fully silicided gate electrode with a predetermined silicide composition.

[0017] With the method for fabricating a semiconductor device according to the present invention, in the second-gate-electrode formation portion, only the second silicon film can be selectively removed therefrom, and full silicidation is conducted on the first silicon film. On the other hand, in the first-gate-electrode formation portion, full silicidation is conducted on the first and second silicon films. Therefore, two types of fully silicided gate electrodes having different silicide compositions can be formed with a good repeatability.

[0023] Preferably, in the above case, the step (c1) is the step of forming, over the first region, a mask film covering the first-gate-electrode formation portion, and then selectively removing, using the mask film as an etching mask, the second protective film of the second-gate-electrode formation portion to expose the second silicon film. With this method, the second protective film can be allowed to remain reliably in the first-gate-electrode formation portion, so that etching of the second silicon film can be reliably blocked in the first-gate-electrode formation portion.

[0025] Preferably, in the method for fabricating a semiconductor device according to the present invention, the step (c) includes: the step (c1) of removing the second protective film of the first-gate-electrode formation portion to expose the second silicon film, and removing the second protective film of the second-gate-electrode formation portion to expose the second silicon film; the step (c2) of forming, after the step (c1), a mask film over the first region, the mask film covering the second silicon film of the first-gate-electrode formation portion; and the step (c3) of selectively etching, using the mask film as an etching mask, the second silicon film and the first protective film of the second-gate-electrode formation portion to expose the first silicon film. With this method, the first protective film does not have to be allowed to remain in the first-gate-electrode formation portion. Therefore, the first-protective-film etching step can be simplified.

Problems solved by technology

However, only replacement of a polysilicon gate electrode of a transistor with a FUSI gate electrode will rather cause a change in the threshold voltage of the transistor due to the work functions of the gate electrodes.

This makes it difficult for each of a p-channel MIS (metal-insulator-semiconductor) transistor and an n-channel MIS transistor to secure a predetermined threshold voltage.

The conventional method for forming a fully silicided gate electrode, however, has a problem that since the thickness of the polysilicon film is adjusted by etching, the adjusted film thickness widely varies.

This leads to variation in threshold voltage and gate resistance.

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